Evolution of Supermassive Black Hole Feedback in Galaxy Clusters

Abstract

Galaxy clusters, the largest gravitationally-bound structures in the Universe, are superb laboratories for studying the baryon cycle that governs the evolution of all galaxies. The outer boundary of a galaxy’s circumgalactic medium (CGM) should be the most sensitive probe of inflowing and outflowing material, but it is difficult to observe. Only in galaxy clusters, where the CGM gets hot enough to glow in X-rays, can the entire baryon cycle be observed– from the rapid cooling of the intracluster medium (ICM) that contributes to the CGM and level of star formation in the central galaxy, to the eventual feeding and triggering of feedback from the largest supermassive black holes (SMBHs) residing in them. This cooling and subsequent feedback from these active galactic nuclei (AGN) is the primary driver of the baryon cycle and evolution of the largest, brightest cluster galaxies (BCGs), quenching their expected levels of cooling and star formation by up to two orders of magnitude. In this thesis, I investigate how the AGN feedback cycle behaved in the early universe, where studies of this kind have not been possible until just recently. Using multiwavelength observations from radio to optical and X-ray, I study a unique, representative sample of galaxy clusters and their central galaxies and SMBHs spanning almost 10 Gyr of cosmic evolution. By studying how the largest galaxies and black holes in the universe co-evolve under extreme and chaotic environments, we can gain a great deal of insight into how the universe we see around us today came to be.